1. Field of the Invention
The present invention relates to a so-called tool holder to be used for mounting a tool, a workpiece and the like on a proper machine and instrument such as a machine tool and a cooling apparatus for the tool holder.
2. Description of Prior Art
A tool holder is generally assembled into a proper machine and instrument such as a machine tool (hereinafter to be called xe2x80x9cmachine toolxe2x80x9d) in a state that the tool or the workpiece is attached to the tool holder. Consequently, the tool holder is subjected to a temperature up by a temperature rising of a workpiece due to machining of the workpiece. Particularly, in case of friction welding, the temperature of a tool or a workpiece rises to 1000xc2x0 C. or so, resulting in a temperature up of a tool holder used for such friction welding to about 500 to 700xc2x0 C.
When the temperature of a tool holder becomes high as mentioned above, a heating value to be transmitted from such a tool holder to the rotation shaft of a machine tool equipped with the tool holder increases, the rotation shaft is heated, and as a result, a bearing supporting the rotation shaft as well as lubricant oil disposed in the bearing is heated, lowering their functions.
It is, therefore, an object of the present invention to effectively control a rise in temperature of a tool holder.
The tool holder according to the present invention comprises a holder body. The holder body includes one or more first fluid passages and one or more second fluid passages. The first and second fluid passages are communicated to each other inside the holder body and open in the outer surface of the holder body.
A cooling fluid such as cooling water and cooling oil is supplied to either the first fluid passage or the second fluid passage and flows through the communicating portion of the first and second fluid passages into the other of the first and second fluid passages, finally to run out of the holder body.
The cooling apparatus of the present invention comprises a fluid guide for guiding the cooling fluid to a tool holder. The tool holder includes a holder body having one or more first fluid passages and one or more second fluid passages. The first and second fluid passages are communicated to each other inside the tool holder and open to the outer surface of the holder body. The fluid guide includes a fitting hole into which the holder body is rotatably fitted, a third fluid passage communicated to the first fluid passage and a fourth fluid passage communicated to the second fluid passage.
In the foregoing cooling apparatus, the cooling fluid is supplied from either the third fluid passage or the fourth fluid passage to either the first fluid passage or the second fluid passage, flows through the communicating portion of the first and the second fluid passages into the other of the first and the second fluid passages, finally to run out into the other of the third and fourth fluid passages.
As mentioned above, according to the tool holder and the cooling apparatus therefor, the tool holder is cooled by the cooling fluid passing the first and the second fluid passages to effectively control its temperature rising.
The first and second fluid passages can be communicated at the central portion of an imaginary circle extending about the axis of the holder body. By doing so, the cooling fluid flows to the center of the holder body, and the center is cooled by the cooling fluid, so that the tool holder is effectively cooled, and a rise in its temperature is more effectively controlled.
The area where the first and second fluid passages are formed has an outer periphery, and the first and second fluid passages can open to the outer periphery of the area. Thereby, supplying and discharging of the cooling fluid relative to the first and second fluid passages can be done from the outer periphery side of the area.
Each of the first and second fluid passages can include a plurality of fluid passages extending in the radial direction of an imaginary circle extending about the axis of the holder body and communicated to each other at the central portion of the imaginary circle. Thereby, since the holder body is cooled over a wide range within a cross section orthogonal to its axis, heat insulation is done effectively in the holder body, which remarkably reduces the heating value transmitted to the rotation axis attaching the tool holder.
In the cooling apparatus, the area of the holder body where the first and second fluid passages are formed has an outer periphery, the first and second fluid passages open, and the fluid guide can be provided with a first groove extending around the area and opening into the fitting hole so as to have the third fluid passage communicate to the first fluid passage, and with a second groove extending around the area and opening into the fitting hole so as to have the fourth fluid passage communicate to the second fluid passage. This facilitates making the first and second grooves for having the first and second fluid passages respectively communicate to the third and fourth fluid passages.
The cooling apparatus can further include a plate-like ring disposed in the fluid guide on the side where the tool is mounted on the holder body, part of the holder body extending through the ring. The ring can include an annular fluid passage extending around the part of the holder body and opening to the side of the fluid guide. Further, the fluid guide can include a first communicating passage for communicating the first fluid passage and the annular fluid passage, and a second communicating passage for communicating the second fluid passage to the annular fluid passage. This enables to absorb part of the heat transmitted from the tool to the fluid guide, to cool the fluid guide by the fluid flowing in the annular fluid passage, thereby cooling the fluid guide, too, effectively.
The cooling apparatus can further include a first and a second nipples connected with the fluid guide so as to have the third and fourth fluid passages respectively communicate to a fluid supply passage and a fluid discharge passage, and a block having a first and a second fitting holes into which the first and the second nipples are fitted. This enables to mount the cooling apparatus on the machine tool by pre-assembling the block into the machine tool and then fitting the nipples into the block.
The holder body can be rotatably received in the fluid guide by the bearing at a position on the side opposite to the tool from the area where the first and second fluid passages are formed, thereby protecting the bearing and the lubricant oil disposed therein from the heat of the tool.